java这个if-else语句中有什么错误吗？

Question

当我打印邮件内容时，尽管displaybmi不是<；十九,

public String BMImessage(){
    SharedPreferences customSharedPreference = getSharedPreferences(
            "myCustomSharedPrefs", Activity.MODE_PRIVATE);

    String Height = customSharedPreference.getString("heightpref", "");
    String Weight = customSharedPreference.getString("weightpref", "");

    float weight = Float.valueOf(Weight);
    float height = Float.valueOf(Height);

    float displaybmi = weight/(height*height);
    if (displaybmi <19) 
        message = "Underweight" ;
    else if (displaybmi >=19 && displaybmi <=25) 
        message = "Desirable Weight";
    else if (displaybmi >=26 && displaybmi <=29) 
        message =  "Overweight" ;
    else if (displaybmi >=30 && displaybmi <=40) 
        message =  "Obese";
    else if (displaybmi >40) 
        message = "Extremely Obese" ;
    return message;
}

Answer 1

还要仔细检查你的计算：

float displaybmi = weight/(height*height);

如果你的体重以千克为单位，身高以米为单位，这个方法就有效。如果您的体重以磅为单位，身高以英寸为单位，则需要添加换算系数：

float displaybmi = (weight * 703.0)/(height * height);

Calculate-Your-Body-Mass-Index

Answer 2

体重指数的值是多少？尝试将比较更改为使用19.0，以确保没有发生截断。您正在将float（displaybmi）与int（19）进行比较，这可能会导致不良行为

Answer 3

如果要比较两个浮点数，可以使用Float.compare(float f1, float f2)

if (Float.compare(displaybmi, 19) < 0) 
    message = "Underweight" ;
else if (Float.compare(displaybmi, 19) >= 0 && Float.compare(displaybmi, 25) <= 0)
...

报告说：

Compares two Float objects numerically. There are two ways in which comparisons performed by this method differ from those performed by the Java language numerical comparison operators (<, <=, ==, >=, >) when applied to primitive float values:

• Float.NaN is considered by this method to be equal to itself and greater than all other float values (including Float.POSITIVE_INFINITY).
• 0.0f is considered by this method to be greater than -0.0f. This ensures that the natural ordering of Float objects imposed by this method is consistent with equals.